Are ring scotomas around fixation a common feature in patients with Acute Idiopathic Blind Spot Enlargement (AIBSE)?

Ring Scotomas in Acute Idiopathic Blind Spot Enlargement Syndrome (AIBSE)

Ring scotomas around fixation are not a common feature in Acute Idiopathic Blind Spot Enlargement Syndrome (AIBSE). The characteristic visual field defect in AIBSE is an enlarged blind spot without ring scotomas around central fixation.

Characteristic Visual Field Defects in AIBSE

AIBSE presents with specific visual field abnormalities:

• Unilateral enlargement of the physiological blind spot 1
• Arcuate scotoma associated with the blind spot 2
• Well-demarcated scotoma centered on the blind spot, with margins that may extend to within 5 degrees of fixation 3
• Variable size and density of the enlarged blind spot 4

Diagnostic Features of AIBSE

AIBSE has several distinguishing features:

• Predominantly affects young adults, with a notable predilection for women 4
• Acute onset photopsia (shimmering lights) in the affected eye 1, 5
• Normal or near-normal visual acuity in many cases 4
• Minimal or no optic disc changes on funduscopic examination 1
• Possible dyschromatopsia and afferent pupillary defects 4
• No P100 latency delay in visual evoked potentials 1

Imaging and Diagnostic Testing

Modern imaging has improved our understanding of AIBSE:

• Spectral domain OCT reveals marked peripapillary changes in the ellipsoid zone 1
• Abnormal autofluorescence corresponding to faint blurring of the optic disc margin 1
• Multifocal electroretinogram (mfERG) shows reduced responses in areas corresponding to the scotoma 2, 3
• Full-field electroretinogram results are typically normal 4
• Focal electroretinogram results are frequently abnormal 4

Pathophysiology and Structural Changes

AIBSE affects specific retinal layers:

• OCT shows disruption of the middle cone outer segment tip line between the IS/OS line and retinal pigment epithelium in affected areas 2
• The external limiting membrane and IS/OS line often remain intact 2
• The disease primarily affects the peripapillary retina 4
• AIBSE is now recognized as a disease of the outer retina 1

Clinical Course and Management

The prognosis and management of AIBSE:

• Photopsia typically decreases over time 4
• Visual field defects often persist, with limited improvement 4
• Some patients may experience full recovery of symptoms within 6-7 months 1
• Follow-up OCT may show restoration of outer retinal layers 6-12 months after disease onset 1
• Early corticosteroid treatment may support outer retinal reorganization 1
• Recurrence can occur in some patients 4

Differential Diagnosis

AIBSE must be distinguished from:

• Optic neuritis (common misdiagnosis) 6
• Multiple evanescent white dot syndrome 6, 4
• Acute zonal occult outer retinopathy (AZOOR) - AIBSE is often considered part of the AZOOR spectrum 5
• Central serous chorioretinopathy 6

Monitoring and Follow-up

For patients with AIBSE:

• Regular monocular Amsler grid testing to detect changes 6
• Scheduled follow-up examinations to monitor visual fields 6
• OCT monitoring to assess outer retinal layer restoration 1

Common Pitfalls in Diagnosis

• Misdiagnosis as optic neuritis due to low awareness of AIBSE 1
• Failure to perform OCT, which has become the gold standard for diagnosing AIBSE 1
• Not recognizing the characteristic peripapillary involvement 4